The 3rd generation partnership project (3GPP) is a project that discusses and prepares specifications of a mobile communication system based on a network evolved from Wideband-Code Division Multiple Access (W-CDMA) and Global System for Mobile Communications (GSM). In the 3GPP, the W-CDMA system is standardized as a third generation cellular mobile communication system, and services are sequentially launched. Moreover, High-speed Downlink Packet Access (HSDPA) having a higher communication speed is also standardized, and its service is launched. In the 3GPP, a study is in progress on the evolution of a third generation radio access technology (hereinafter referred to as “Long Term Evolution (LTE)” or “Evolved Universal Terrestrial Radio Access (EUTRA)”) and on a mobile communication system realizing a higher-speed data transmission and reception by use of a wider frequency band (hereinafter referred to as “Long Term Evolution-Advanced (LTE-A)” or “Advanced-EUTRA”).
As the communication system in the LTE, an examination is being performed on an Orthogonal Frequency Division Multiple Access (OFDMA) method in which subcarriers orthogonal to each other are used to perform user multiplexing and an Single Carrier-Frequency Division Multiple Access (SC-FDMA) method. That is, in a downlink, the OFDMA method, which is a multicarrier communication method, is proposed, and in an uplink, the SC-FDMA method, which is a single carrier communication method, is proposed.
On the other hand, as the communication system in the LTE-A, an examination is being performed, in a downlink, on the OFDMA method and, in an uplink, on the introduction of a Clustered-Single Carrier-Frequency Division Multiple Access (clustered-SC-FDMA, also referred to as a DFT-s-OFDM with spectrum division control or a DFT-precoded OFDM) in addition to the SC-FDMA method. Here, the SC-FDMA method and the clustered-SC-FDMA method, which are proposed as the uplink communication method in the LTE and the LTE-A, are characterized in that, due to the characteristic of a single carrier communication method (due to a single carrier characteristic), it is possible to suppress low a Peak to Average Power Ratio (PAPR: a transmit power) when data (information) is transmitted.
Although a frequency band used in a general mobile communication system is contiguous, in the LTE-A, it is considered to compositely use a plurality of contiguous and/or non-contiguous frequency bands (hereinafter referred to as a “Component Carrier (CC)” or a “Carrier Component (CC)”), to operate the frequency bands as one frequency band (a wide frequency band) (Frequency band aggregation: also referred to as Carrier aggregation, Spectrum aggregation, Frequency aggregation or the like). Furthermore, it is also proposed that, in order for a base station apparatus and a mobile station apparatus to use a wide frequency band more flexibly to communicate with each other, a frequency band used in a downlink communication is made to differ in frequency bandwidth from a frequency band used in an uplink communication (Asymmetric frequency band aggregation: Asymmetric carrier aggregation) (non-patent document 1).
FIG. 9 is a diagram illustrating a carrier-aggregated mobile communication system in a conventional technology. That, as shown in FIG. 9, a frequency band used in a downlink (DL) communication and a frequency used in an uplink (UL) communication have the same bandwidth is also referred to as Symmetric frequency band aggregation. As shown in FIG. 9, a base station apparatus and a mobile station apparatus compositely use a plurality of component carriers that are contiguous and/or non-contiguous frequency bands, and thus they can communicate with each other in a wide frequency band composed of a plurality of component carriers. FIG. 9 shows as an example that a frequency band (also referred to as a DL system band or a DL system bandwidth) used in a downlink communication having a bandwidth of 100 MHz is composed of five downlink component carriers (DCC1: Downlink Component Carrier 1, DCC2, DCC3, DCC4 and DCC5) each having a bandwidth of 20 MHz. FIG. 9 also shows as an example that a frequency band (also referred to as a UL system band or a UL system bandwidth) used in an uplink communication having a bandwidth of 100 MHz is composed of five uplink component carriers (UCC1: Uplink Component Carrier 1, UCC2, DCC3, DCC4 and DCC5) each having a bandwidth of 20 MHz.
As shown in FIG. 9, on each of the downlink component carriers, downlink channels such as a Physical Downlink Control Channel (PDCCH) and a Physical Downlink Shared Channel (PDSCH) are mapped. The base station apparatus allocates, to the mobile station apparatus using the PDCCH, control information (such as resource allocation information, Modulation and Coding Scheme (MCS) information, Hybrid Automatic Repeat Request (HARQ) processing information for transmitting a downlink transport block that is transmitted using the PDSCH, and transmits, using the PDSCH, the downlink transport block to the mobile station apparatus. In other words, in FIG. 9, the base station apparatus can transmit up to five downlink transport blocks to the mobile station apparatus in the same sub-frame.
On each of the uplink component carriers, uplink channels such as a Physical Uplink Control Channel (PUCCH) and a Physical Uplink Shared Channel (PUSCH) are mapped. The mobile station apparatus uses the PUCCH and/or the PUSCH to transmit, to the base station apparatus, Uplink Control Information (UCI) such as control information of the HARQ (hereinafter described as HARQ control information), channel state information and a scheduling request. Here, the HARQ control information includes information that indicates Positive Acknowledgment/Negative Acknowledgment (ACK/NACK, ACK or NACK) for the PDCCH and/or the downlink transport block and/or information that indicates Discontinuous Transmission (DTX). The information indicating the DTX is information which indicates that the mobile station apparatus has failed to detect the PDCCH transmitted from the base station apparatus.
Here, in FIG. 9, downlink/uplink component carriers where any one of the downlink/uplink channels such as the PDCCH, the PDSCH, the PUCCH and the PUSCH is not mapped may be present.
Likewise, FIG. 10 is a diagram illustrating an asymmetrically carrier-aggregated mobile communication system in the conventional technology. As shown in FIG. 10, in a base station apparatus and a mobile station apparatus, a frequency band used in a downlink communication differs in bandwidth from a frequency band used in an uplink communication, and the base station apparatus and the mobile station apparatus compositely use component carriers that are contiguous and/or non-contiguous frequency bands constituting these frequency bands and can communicate with each other in a wide frequency band. FIG. 10 shows as an example that a frequency band used in a downlink communication having a bandwidth of 100 MHz is composed of five downlink component carriers (DCCT, DCC2, DCC3, DCC4 and DCC5) each having a bandwidth of 20 MHz. FIG. 10 also shows that a frequency band used in an uplink communication having a bandwidth of 40 MHz is composed of two uplink component carriers (UCC1 and DCC2) each having a bandwidth of 20 MHz.
In FIG. 10, on each of the downlink/uplink component carriers, a downlink/uplink channel is mapped, and the base station apparatus uses the PDCCH to allocate the PDSCH to the mobile station apparatus, and uses the PDSCH to transmit the downlink transport block to the mobile station apparatus. In other words, in FIG. 10, the base station apparatus can transmit up to five downlink transport blocks to the mobile station apparatus in the same sub-frame. Moreover, the mobile station apparatus uses the PUCCH and/or the PUSCH to transmit, to the base station apparatus, uplink control information such as the HARQ control information, the channel state information and the scheduling request.
In the LTE-A, an allocation method is proposed in which the base station apparatus uses the PDCCH on the downlink component carrier to allocate the PDSCH to the mobile station apparatus (non-patent document 2).
FIG. 11 is a diagram illustrating an example of the method of using the PDCCH to allocate the PDSCH in the conventional technology. FIG. 11 shows part (part of DCC1, DCC2 and DCC3) of the downlink component carrier in FIGS. 9 and 10. As shown in FIG. 11, the base station apparatus uses a plurality of PDCCHs on one downlink component carrier, and thereby can allocate a plurality of PDSCHs to the mobile station apparatus in the same sub-frame.
FIG. 11 shows as an example that the base station apparatus uses three PDCCHs (PDCCHs respectively indicated by oblique lines, grid lines and mesh lines) on DCC2, to allocate PDSCHs on DCC1, DCC2 and DCC3 (the PDSCH on DCC1 is allocated by the PDCCH indicated by the oblique lines, the PDSCH on DCC2 is allocated by the PDCCH indicated by the grid lines and the PDSCH on DCC3 is allocated by the PDCCH indicated by the mesh lines). The base station apparatus uses the PDSCHs on DCC1, DCC2 and DCC3, and thereby can transmit up to three downlink transport blocks to the mobile station apparatus in the same sub-frame.    Non-patent document 1: “Carrier aggregation in LTE-Advanced”, 3GPP TSG RAN WG1 Meeting #53bis, R1-082468, Jun. 30-Jul. 4, 2008.    Non-patent document 2: “PDCCH Design of Carrier Aggregation”, 3GPP TSG RAN WG1 Meeting #57, R1-091829, May 4-8, 2009.